The WHO defines health as ... a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity. In fact, the notion that mental health and, in particular, subjective well-being (SWB) is an important proxy for social welfare is gaining considerable policy traction, with the OECD and the European Union supporting initiatives to use SWB to supplement or even replace traditional measures of progress such as GDP. While great strides have been made in developing measures of SWB and documenting their relationship with macro and micro-level variables, far less is understood about the impact of institutional factors, such as health insurance, on these measures. I propose a research agenda that will advance our knowledge of how health insurance impacts mental health - defined here as not only the absence of mental illness but also the presence of SWB - of the elderly. Recent evidence suggests the effects may be quite large: two recent randomized experiments have shown that gaining health insurance reduces the probability of screening positive for depression by 14-30%. With only a few measures of SWB and small sample sizes, however, these experiments can shed only limited light on the pathways through which health insurance affects mental health. My proposed work will fill in this gap in knowledge. I will focus on two pathways. The first and most straightforward pathway is an increase in utilization of mental health treatments, including medications, due to insurance. The other mechanism, which has received significantly less attention, relates to exposure to risk, stress and worry. Health insurance reduces exposure to catastrophic out-of-pocket medical expenditure risk and related financial strain substantially. My previous work finds that reductions in medical financial strain due to Medicare are largest among low-educated populations. Health insurance is also likely to reduce stress related to access to health care and to overall health. The elderly is the population for which this stress channel is probably most important: they have higher rates of healthcare utilization, larger out-of-pocket expenditures and higher risk of catastrophic spending. The K01 Mentored Research Scientist Development Award will allow me to build on my existing research strengths and to expand my work on health insurance coverage through Medicare to include SWB and mental health, areas in which I have no previous training. To ensure the success of the proposed work, I will be mentored by a diverse group of renowned scholars, with expertise in psychology, psychiatry, health services, health policy and economics, and behavioral economics. These researchers will guide me through a detailed training plan which includes guided readings, formal coursework and professional seminars and conferences. Such research agenda will help me reach my long-term career goal to establish myself as a health economist specializing in health insurance and its impact on individual outcomes, including mental health; successfully develop further research projects as an independent scientist; and become a key researcher in this field.